Non-optic vision: Beyond synesthesia?

Area of Science:

• Neuroscience
• Sensory Perception
• Vision Science

Background:

• S-cone syndrome, a degenerative retinal disorder, caused blindness in a 28-year-old female (NS) in her early twenties.
• Post-blindness, NS developed unusual sensory experiences involving visual perceptions linked to tactile and proprioceptive input.

Observation:

• NS reported automatic, consistent visual perceptions of her hands and touched objects, mediated by head position.
• These perceptions were involuntary and influenced by her prior visual experiences, indicating significant top-down processing.
• The visual experiences accurately represented her hands and objects, extending to inferred surroundings.

Findings:

• The patient's visual experiences were distinct from mental imagery due to their automaticity and proprioceptive mediation.
• Unlike previously reported cases of acquired synesthesia, NS exhibited remarkable complexity and a high degree of top-down influence.
• The findings suggest a potential novel phenomenon exceeding the current understanding of synesthesia.

Implications:

• This case challenges existing models of sensory substitution and cross-modal plasticity.
• It highlights the brain's capacity for generating complex, veridical perceptions in the absence of primary sensory input.
• Further research into NS's condition could offer insights into visual perception, proprioception, and the brain's adaptive capabilities.